UNITED STATES
NUCLEAR REGULATORY COMMISSION
WASHINGTON, D. C. 20555
November 8, 1985
TO ALL LICENSEES WITH BABCOCK AND WILCOX OPERATING REACTORS
Gentlemen:
SUBJECT: RESOLUTION OF GENERIC ISSUE 69: HIGH PRESSURE INJECTION/MAKE-UP
NOZZLE CRACKING IN BABCOCK AND WILCOX PLANTS (Generic Letter
85-20)
On January 24, 1982, an unexplained loss of coolant was detected during
normal plant operation at Crystal River Unit 3. After an orderly shutdown,
an inspection of the reactor coolant and associated systems revealed that
the high pressure injection/makeup (HPI/MU) check valve, valve-to-safe-end
weld, safe-end, and the mal sleeve were cracked. Subsequently, inspections
were performed at other B&W designed plants. Most of these inspections
revealed similar types of cracking in the HPI system of the facilities which
indicated that the cracking problem was a generic one. A Safe-End Task Force
was formed by the B&W Owners' Group to compile pertinent facts and to make
recommendations to solve the cracking problem. The Task Force completed its
work in late 1982 and provided its findings and recommendations to the
Owners' Group in the "Babcock and Wilcox 177 Fuel Assembly Owners' Group
Safe-End Task Force Report on Generic Investigation of HPI/MU Nozzle
Component Cracking."
The staff reviewed the Task Force recommendations and agreed that the
following actions be taken to resolve this issue:
(1) Reroll the upstream end of the thermal sleeve when inspections indicate
that a gap exists or repair and/or replace damaged components;
(2) Implement an augmented inservice inspection plan; and
(3) Perform a detailed stress analysis of a nozzle with a modified thermal
sleeve design to justify long term operation.
All participants in the Owners' Group Task Force have performed the
recommended repairs to damaged components (Recommendation 1) and have
voluntarily implemented a satisfactory augmented inservice inspection
program (Recommendation 2). Performance of a stress analysis (Recommendation
3) is required to maintain original licensing commitments regarding the
stress and fatigue usage allowables required by USAS B31.7 or the ASME code.
Analyses for modified nozzles have been performed; analyses for nozzles not
requiring modification should have been performed before licensing.
Operating experience for some plants has indicated that the expected fatigue
analyses could be substantially exceeded by the end of life. For example, an
increased number of HPI actuation transients could occur due to manual
actuation after reactor trips to avoid losing pressurizer level. Therefore,
the staff has determined that it is necessary to ensure that valid stress
analyses have been performed.
8511050057
November 8, 1985
- 2 -
Each licensee should verify that a valid stress analysis has been performed
for HPI/MU nozzles in accordance with its licensing commitments to meet the
Code requirements. Also, each licensee should verify that the cumulative
fatigue usage for these nozzles is within the allowables based on a
realistic projection of the thermal cycles expected for the life of the
plant. The information including stress analysis results and expected number
of thermal cycles should be maintained for future inspection.
This generic letter does not impose any new regulatory requirements or any
reporting requirements. Therefore, no clearance from the Office of
Management and Budget is required. If you have any questions, the staff
contact John Hannon who can be reached at (301) 492-8543.
Hugh L. Thompson, Jr., Director
Division of Licensing
cc: List of Generic Letters